Dynamic Line Management (DLM) is a technique for improving the stability of DSL connections. (NB The term “xDSL” is sometimes used to refer to any of an increasing family of DSL technologies, but the term “DSL” will in general be used here). DLM is particularly useful when operating DSL connections at close to their maximum speed, because under these conditions external noise affecting the transmitted signal can cause the transceivers to be unable to successfully recover the signal to be transmitted with sufficient reliability to enable the connection to be maintained. If this occurs, the connection needs tote re-established. This is referred to as a re-synch or a re-train and the user notices a temporary loss of service while the connection is re-established. Re-synchs are generally found to be particularly annoying by end-users.
DLM seeks to minimise re-synchs by automatically analysing DSL connections (especially the rate of occurrence of re-synchs) and varying certain parameters which can affect the likelihood of re-synchs occurring (for example the depth of interleaving, the amount of redundancy built into the encoding used, etc.). Typically, this is done by using a number of different “profiles” having various different sets of values for the parameters most likely to have an impact on the stability or otherwise of DSL connections and moving a particular connection between different profiles until a profile is found which provides an acceptable stability. The profiles are applied at the local exchange (sometimes referred to—especially in the USA—as the Central Office) usually within a piece of equipment known as a Digital Subscriber Line Access Multiplexer (DSLAM) which houses a number of DSL transceiver units as is well known in the art.
Typically, the profiles are conceptually able to be thought of as ranging between “more aggressive” and “less aggressive”, where the more aggressive profiles tend to provide better services to the user in terms of especially higher bit rates and lower latencies, but are more likely to result in the line being unstable, whereas less aggressive profiles tend to offer lower bit rates and/or latencies but greater stabilities.
An Alcatel Technology White Paper from April 2005 entitled “Dynamic Line Management for Digital Subscriber Lines” previously available at the following URL: http://www1.alcatel-lucent.com/com/en/appcontent/apl/18812_DLM_twp_tcm172-228691635.pdf discusses DLM and suggests in overview an implementation in which there is a “Validation” phase and an “Operations” phase. In the Validation phase a connection is monitored fairly intensively to identify an appropriate profile for the line and thereafter it is monitored less intensively to ensure that the originally selected profile continues to remain valid.
International patent application WO2008/093045 describes an earlier DLM solution devised by the present applicants in which very unstable data connections are detected in an efficient manner and corrective action is taken within a relatively short period of time whilst data connections which are not very unstable are monitored and transitioned between different profiles based on more thorough monitoring over a longer time-scale.
DLM solutions such as those above use, as at least one of the metrics used in monitoring the performance of a line, the number of re-trains or re-synchs occurring on a line within a predetermined period of time. In view of the fact that this metric can in certain circumstances be misleading, International patent application WO2009/081131 proposed a technique intended to allow for a more reliable metric of line performance to be provided. The technique disclosed involves processing data on the number of re-trains or re-synchs occurring on a line within a predetermined period of time in order to take account of the possibility that some re-synchs may be caused (i.e. intentionally) by user action rather than as a result of the line experiencing technical problems or instability.
International patent application WO20091081129 describes another DLM technique devised by the present applicants in which a stability level is associated with each data connection, specifying a desired level of stability for that data connection. The customer may then be offered a choice between a plurality of different levels of stability, each of which may be suitable for a different type of activity. The stability level may be chosen by the user of the data line in question, or chosen on their behalf by their service provider in dependence on an indication of the application the user is determined to be using. Alternatively, service providers may simply select a stability level on behalf of their customers.
Referring now to other prior art techniques, U.S. Pat. No. 7,830,955 relates to managing digital communication systems, and to adaptive control of various transmission parameters, such as maximum transmit power spectral density, maximum aggregate transmission power, transmission band preference, minimum and maximum receiver margin, frequency-dependent bit-loading and power controls and/or bit-loading restrictions in communication systems such as DSL systems. In particular, it suggests that configuring the parameters of a DSL system related to power, band usage and margin may be done based on collected operational data, collected for a DSL system operating under a known configuration and/or profile. A target profile is selected based on binder-level information, which can include deployment point information, topology information, and/or crosstalk coupling information.
United States application US2009207985 also relates to digital communication systems, and relates specifically to managing distributed and/or bonded vectored DSL systems. It discusses how a controller such as a DSL management entity, a “Spectrum Management Center” (SMC) or otherwise can be used to collect and analyse operational data and/or performance parameter values, and refers to an example in which the SMC determines the maximum safe data rate at which the line can operate with acceptably low probability of service disruption, loss, or customer complaint. In calculating the best data rates, the SMC can incorporate the service providers' products (i.e. data rates and quality of service requirements at those data rates, which are also a function of the customer service selection and willingness to pay), billing management, and general provisioning practice and coordination with operations, and can supply the profile along with any vectoring information to the DSL line for implementation by the DSLAM or an element management system.
Typically, Dynamic Line Management is implemented by an entity such as a network operator in respect of data connections used by end-users who are in fact (direct) customers of Internet Service Providers (ISPs) or other such communication providers, rather than (direct) customers of the network operator. While techniques such as those referred to above allow a network operator to implement DLM in a manner that reacts in a variety of ways to criteria such as performance data and desired stability levels for each data connection, network operators have so far implemented DLM for the data connections they handle using a single DLM engine. Although such a DLM engine may operate against a set of possible thresholds, which may be configurable on a line-by-line basis, the root DLM engine has therefore generally been the same for each communication provider for which the network operator is implementing DLM.
In particular, it will be noted that none of the prior techniques discussed above suggest taking account of a service-provider-associated category (in addition to the usual performance data) in the profile-updating decision.